The invention is an improvement on the class of disc brakes exemplified by U.S. Pat. No. 3,863,038 of Jan. 28, 1975 and other patents. Brakes of this class are used primarily in power transmission trains between hydraulic drive motors and gear speed reducers.
Customarily, the prior art disc brakes are biased by a spring means to the engaging or "on" condition and are released by the action of a hydraulically-operated piston which engages a stator disc to move it axially in opposition to the spring means so as to release the pressure between the rotor and stator discs of the assembly. While such prior art brakes differ considerably in mechanical configuration, insofar as is known, they all operate on the above-stated principle and are of the "single acting" type in terms of being released by the movement of the hydraulically-operated piston and engaged by the opposing spring means. That is to say, the prior art brakes have a rather sudden and direct on-off operational mode, which in most applications is an excessively sudden or abrupt brake action which does not impart a desirable soft "feel" to the system.
With the above problem in mind, it is the object of this invention to provide an improved disc brake which is double-acting in terms of its "on" and "off" mode of operation, and as a result the sudden, abrupt or jerky brake action of the prior art is totally eliminated and replaced by a smooth and soft action imparting an ideal operational "feel" to the brake system for the operator which is highly desirable in many application. In addition, this improved disc brake can be utilized as a "normally engaged" or as a "normally disengaged" brake.
More particularly, the invention employs coacting hydraulically operated brake releasing and brake applying movable pistons in separated fluid chambers of a disc brake housing. In an intervening dry chamber, the rotor and stator brake discs are arranged between the two pistons. The brake release piston has an axially extending annular skirt which surrounds the brake discs and has its far end engaging a brake pressure plate which constitutes one endmost stator disc of the brake assembly. The pressure plate is engaged on its side away from the brake release piston by springs which are intervened between the pressure plate and the brake applying piston. These springs bias the brake to an engaged condition and thus provide a fail-safe capability for the disc brake even when there is no normal operating pressure behind the brake applying piston. When the brake applying piston is pressurized or activated, such piston can override the force of the brake release piston and the springs to more positively and directly apply the disc brake.
The brake release piston is pressurized by normal machine operating pressure sufficient only to release the brake against spring action. The pressure on the release piston is easily overriden by the action of the engaging piston when the latter is pressurized by foot pedal or hand lever means under control of a machine operator who wishes to apply the brake.
Another significant feature of the invention lies in the provision of a threaded adjusting collar allowing the disc elements to be adjusted periodically to compensate for wear. The adjusting collar is lockable and is in a protected position within the housing of the brake but readily accessible at one end of the assembly.
Other features and advantages of the invention over the prior art will become apparent during the course of the following description.